1. Field of the Invention
The present invention relates to a disazo compound or a salt thereof and a polarizing film using the disazo compound or the salt thereof, and specifically to a disazo compound or a salt thereof, which covers a wavelength with a range of 520 to 580 nm in the case of being used as a polarizing element, and a polarizing film using the disazo compound or the salt thereof.
2. Prior Art
A dye-based polarizing film is manufactured in such a manner that a base material for polarizing film, such as a oriented polyvinyl alcohol-based film or polyene-based film which is obtained by orienting polyene produced through dehydrochlorination of polyvinyl chloride film or dehydration of polyvinyl alcohol-based film, to which is added a dye that covers a desirable wavelength as a polarizing element. For example, a compound having the following structure is described in WO 00/37973 as dye, which covers a wavelength with a range of 520 to 580 nm in the case of being used as a polarizing element.

The polarizing film, which is obtained by using the above-mentioned disazo compound, however, has not necessarily been satisfactory from the viewpoint of light resistance and initial polarizing performance, particularly light resistance.